The present invention relates generally to an integrated circuit and, more specifically, to an integrated circuit chip with built-in self-test (BIST) capability.
In recent years, built-in self-test (BIST) circuitry has been incorporated within integrated circuit (IC) chips to facilitate testing without the need for complex external test equipment. The advantages of BIST are that no special test patterns or test equipment are required and the integrated circuits can be tested independent of environment.
FIG. 1 illustrates a conventional IC chip 10 including a BIST unit 12 and circuitry 14, the latter of which can be memory elements and/or logic circuits. The BIST unit 12 applies a test condition 16 to the circuitry 14 and, at the conclusion of the self-test, checks the return value 18 emitted from the circuitry 14. If the return value 18 is different from that expected, there will be at least one defect in the circuitry 14. Provision of the BIST capability within an IC chip enables defects or other problems that might arise in the operation of the circuit to be identified, whereas conventional BIST circuitry only determines if the quality of the IC chips is satisfactory.
On the other hand, the IC chips are designed to work properly at a default operating frequency. Furthermore, the IC chips are set at the default operating frequency plus some design margin, although the design margin is not necessary on most IC chips. In other words, if the IC chips function at a higher operating frequency than the default, the chips may improve their overall performance. However, in some extreme cases, some chips may work at a lower operating frequency than the default, as a result of quality deficiency.
Accordingly, there is a need to provide an apparatus that utilizes the BIST capability to automatically determine the optimum operating frequency for individual IC chip.
It is one object of the present invention to provide an apparatus to automatically determine the highest operating frequency for individual integrated circuit (IC) chip.
It is another object of the present invention to provide such an apparatus that utilizes the built-in self-test (BIST) capability to improve the performance and stability of individual IC chips.
The foregoing objects are achieved in an apparatus for automatically determining an operating frequency of an IC chip. The apparatus includes a BIST unit, a clock generator, and a frequency determination unit. The BIST unit is provided to test the IC chip. The clock generator provides a test clock for the IC chip. The frequency determination unit sets the clock generator to generate the test clock and determines the operating frequency in accordance with a test result produced from the BIST unit. The frequency determination unit also enables the BIST unit to test the IC chip.
Operationally, the frequency determination unit sets an initial frequency value for the clock generator providing the test clock to the IC chip. Meanwhile, the frequency determination unit enables the BIST unit to test the chip with the test condition. Then, the frequency determination unit detects the test result from the BIST unit after the built-in self-test. If the test result does not satisfy certain criteria, the frequency determination unit will tune the frequency value and set the clock generator to generate the test clock corresponding to the tuned frequency. Again, the BIST unit tests the IC chip. The apparatus repeats the tuning and testing steps until the test result has satisfied the criteria. Finally, for the IC chip, the apparatus determines the highest operating frequency that passes the built-in self-test.